DE1128842B - Process for the production of barium oxide - Google Patents

Description

It is known per se that barium carbonate is replaced by carbon in an inert atmosphere Temperature above about 1000 ° C can be reduced to barium oxide, with during the reaction Carbon monoxide is formed. (If a purge gas is used, this temperature can be increased to around 800 ° C.)

It has also been recommended to carry out the reaction in the melt flow, especially if the barium carbonate produced in the saccharification of molasses is used as the starting material. There this carbonate as a result of heavy contamination by lime, silica and organic substances but has a very high melting point of about 1300 ° C, it must be known Flux, such as fluorspar, soda or borax, add, whereby it succeeds its melting point to about 1200 ° C.

The carbon is only added to the barium carbonate in the molten state, so that the Initiate formation of barium oxide, the presence of the flux to a better Contact between the carbon and the carbonate in the melt flow leads.

However, if the relevant implementation is to be carried out in the solid state, result certain difficulties arise from the fact that the two reactants in one are sufficient must be in close contact with each other, as diffusion is difficult. Experiments with granules, which by pressing out a barium carbonate-carbon mixture and then heating as well as crushing can be obtained, did not give satisfactory results, since the on Particles obtained in this way have an irregular shape and are prone to dusting as a result mechanical abrasion.

This phenomenon is particularly noticeable when looking for the required Heat treatment operated by the known technique of fluidized bed, since the particles in the Fluidized bed are exposed to particularly strong mechanical stress.

Heretofore, the fluidized bed technique has essentially been used for the reaction between gases been, wherein the bed mass serves as a catalyst and / or heat exchanger, such as. B. at the known cracking processes for hydrocarbons.

The solids forming the fluidized bed have also been allowed to react with the carrier gases, such as z. B. in the conversion of calcium carbide with nitrogen to calcium cyanamide. In an implementation,

Process for the production of barium oxide

Applicant:

Laporte Chemicals Limited,
Luton, Bedfordshire (UK)

Representative: Dr. K. Schwarzhans, patent attorney,
Munich 19, Romanplatz 10

Claimed priority:
Great Britain of October 29, 1957 (No. 33 738)

Jack Trask Unwin, Luton, Bedfordshire

(Great Britain),
has been named as the inventor

in which the carrier gas is inert and only those components react with one another which the solid particles are composed of, however, there are particular technical difficulties on, since the reaction on the one hand only takes place completely if there is contact between the two concerned Components in the solid state is intimate enough, while on the other hand a dust formation because of the associated loss of substance must be avoided as far as possible.

Surprisingly, it has now been found that this problem can be solved if the particles to be fluidized, consisting of barium carbonate and carbon, are produced and pretreated in a special way. According to the invention, beads are first formed from an intimate mixture of barium carbonate, at least 5 percent by weight of carbon and at least 0.2 percent by weight of an alkali salt, each based on the amount of the total mixture, and these are calcined at a temperature between 400 and 1000 ° C in an inert atmosphere, whereupon the spheres compacted in this way are fluidized in an inert gas and ^{treated in a manner known per se at temperatures between 800 and 1025 °} C. for the purpose of reducing the barium carbonate to barium oxide.

The beads experience the addition of the alkali salt and the subsequent calcination

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a compaction and hardening, which makes it possible to combine them without disturbing dust formation Treat fluidized bed. This results in particularly high-quality and pure end products obtained with BaO contents of up to 98% without special enrichment or concentration is required.

The alkali salts that are added before the grain is formed are appropriately derived from sodium and potassium

The schematic drawing illustrates a rotating device suitable for forming the beads. In the drawing, Fig. 1 shows a side view of the device and Fig. 2 is a view of part of the device.

According to the drawing, a carbon-barium carbonate mixture, which contains an alkali salt is supplied through an opening 2 to a rotating pipe 1 made of stainless steel. This pipe

rotating sieves 7 and 8. These sieves are concentric arranged to the axis of a rotating shaft 9, which is provided with a belt pulley 10 is. The beads with too large a diameter pass through a tube 11 and a Funnel 12 into a (not shown) collecting vessel. Grains that are too small in diameter will fall through the sieves 7 and 8 through and are over a

or lithium from; Carbonates of the relevant io are heated from the outside by heating devices 3. Metals are preferred. It is carried and driven by two shafts

These alkali salts act as a kind of binding agent 4a and 4b or four rollers 2a, which are arranged on these shafts between the barium carbonate and the carbon. A belt pulley 5 is used by a substance in the formation of the beads and in the sliding (not shown) drive in Rotaansehverbindenden calcination. They can be offset given 15. The rollers on the shaft 4b rotate freely, if before the fluidization from the compressed ones, the shaft 4b , on the other hand, is firmly supported. In order to remove and hard globules, expediently simplification in Fig. 1 is only the shaft 4a by leaching it with water. posed.

The removal of the alkali salts before the reduction The angle at which the tube 1 is placed

in a fluidized bed is particularly recommended in ao, is best determined by preliminary tests, those cases where the salt used is easily changed. The size of the beads obtained depends on both evaporates and therefore there is a risk that the water content of the evaporated through the opening 2 is present Salt in the colder parts of the plant resulted in a mixture also from the angle and from precipitates, causing constipation. the speed of rotation of the tube 1. At the

For the calcination of the alkaline salt-containing spheres leaving the tube 1, the still soft surfaces arrive and for fluidization, each globule is suitable via a shaking device 6 to the gas, which burns the gas contained in the globules and required for the reaction
Carbon, like helium, nitrogen or methane.

The speed of the fluidized gases will
expediently to about 4 times the critical
Gas speed of the fluidized bed adjusted. It
but can also gas velocities up to
at ten times the value of this critical speed 35 funnel 13 in a (not shown) collecting vessel can be used. Since the headed for fluidization. The material which is separated out because of too little or too much gases used act as purging gases at the same time, particle size can also be returned to the process, even at low temperatures. 800 ° C can still be used with success. The beads of the desired size fall

The ratio of carbon to barium 40 through the sieve 7, but not through the sieve 8, and carbonate in the spheres to be fluidized is approximately 6: 100 via a shaking device 14, since below these
Conditions a practically complete reduction
of the existing barium carbonate is ensured
and in addition a maximum of 45 in the end product
There are traces of unreacted carbon.

The most favorable size of the beads is between about 1.204 and 0.353 mm.

It is particularly advantageous if the ball 50 is placed through a guide funnel 17 into a collecting vessel (not made from the intimate mixture of barium). To a burning of the carbonate, carbon and alkali salt that produces
this mixture from top to bottom lengthways
of an inclined, rotating pipe that leads to
heated to a temperature between 100 and 400 ° C 55
is. Those that are formed in this way are still giving way
Beads are sieved, and the fraction with
suitable particle size, e.g. B. with diameters
between 1.2 and 0.35 mm, is further treated in a rotating calcining furnace. 60 was 2.72 to 4.54 kg per hour. The proportion of globules with too small that is obtained when carrying out the grain formation stage carries the most favorable temperature to which the
inclined, rotating tube is heated to about 300 ° C.
Below 100 ° C the water will not be sufficient
expelled quickly, while above 400 ° C a 55
premature undesirable at this stage of the process
Compression of the barium carbonate-carbon mixture occurs.

rotating calcining tube 15 supplied, which is made of stainless There is steel and is mounted and driven in a manner similar to that of the tube 1.

The calcining tube 15 is heated by an electric furnace 16. The beads flow through the Calciner 15 down, compacting and hardening, and they end up being 15a discharged from the calcining furnace. You will then arrive

To prevent carbon, an inert gas, such as nitrogen, is passed through the heating during heating Outlet opening of the tube 15 supplied.

In a typical experiment, the tube was 61 cm long and 15.2 cm in diameter and was set in rotation at 40 revolutions per minute. The working temperature was on Held at 250 to 300 ° C. The throughput of the pipe

Diameter was 25%. The residence time of the carbon-barium carbonate mixture in the pipe was about 10 minutes.

The outer screen 8 had a length of 20.3 cm, its diameter of 10.2 cm and a mesh size of 0.353 mm. The inner sieve 7 had a length of 20.3 cm, a diameter of 4.9 cm

and a mesh size of 1.204 mm. The screen system was rotated at a speed of 44 revolutions per minute and it had a capacity of 2.27 to 4.54 kg per hour. The calciner was 76.2 cm in length, 4.9 cm in diameter, and was heated by an electric furnace of 2 kW. The length of the heated zone was 35.4 cm, the temperature 700 ° C. The calcining furnace was rotated at 32 revolutions per minute and it had a throughput of 1.80 to 3.60 kg per hour. The residence time of the beads in the calciner was about 2 ¹ I ₂ minutes. The incline of the calciner was 1:30.

The following examples illustrate the process of the present invention.

example 1

4.54 kg of barium carbonate were mixed in portions of approximately 0.45 kg each in a small, rotating mixer mixed with a total of 0.30 kg of carbon. The proportion of sodium carbonate in the mixture was 0.9 percent by weight, the moisture content in the mixture was 30 percent by weight. The mixture was then passed through the grain formation plant shown in the drawing. The calcination temperature was 700 ° C. The packing density of the beads before and after calcination was 1.0 or 1.8 g / cm3.

The sieve analysis showed the following:

= 130 + _{18/0 +} 30 = _490/0 + 60 = _370/0 + 85 = 0.20 / ₀ -85 = O, 4O / o

Reduction in a fluidized bed resulted in a product that was 95 to 98% barium oxide contained.

same as in Example 1; the grain formation process was also the same. The packing density of the spheres before and after calcining was 1.0 to 1.8 g / cm ³ . The sieve analysis showed the following:

Example 2

4.54 kg of barium carbonate were mixed with 0.31 kg of carbon according to Example 1. The content of water and sodium carbonate in the mixture was +85 = 0.4O / o -85 = 0.40 / ₀

After reduction in a fluidized bed, the product contained 93 to 96% barium oxide.

In the examples, B.S.S. screens have been used, the meshes of which have the following dimensions exhibited:

18 stitches BSS
30 stitches BSS
60 stitches BSS
85 stitches BSS

0.853 mm
0.500 mm
0.251 mm
0.178 mm

Claims (1)

PATENT CLAIM: Process for the production of barium oxide by reducing a mixture of barium carbonate and carbon at temperatures between 800 and 1025 ° C, using the known technique of the fluidized bed, characterized in that initially from an intimate mixture of barium carbonate, at least 5 percent by weight carbon and at least 0.2 percent by weight of an alkali salt, preferably a carbonate, based in each case on the amount of the total mixture, forms beads, calcines them at a temperature between 400 and 1000 ° C in an inert atmosphere, removes the alkali salt, if necessary by leaching with water, and finally the so compacted beads are fluidized in an inert gas. Considered publications:
German Patent No. 965 992;
Gm el in, "Handbook of Inorganic Chemistry" system no. 30, 8th edition, 1932, p. 79. 1 sheet of drawings © 20? 578/253 4.62